Various user interfaces are known which allow physical human interaction with computer systems, such as personal computers, games consoles and mobile phones. Such user interfaces allow data to be input by the user to the computer system and/or output by the computer system to the user.
For example, touch screens are now commonplace in mobile phones. A touch screen can be used to output data as per a conventional visual display, but also acts as an input device based on the touch of a user either directly or via an additional implement, such as a stylus.
It is also known for touch screens to provide haptic feedback to the user. For example, many mobile phones vibrate when the user touches the screen to provide such haptic feedback and to acknowledge the touch of the user.
WO 01/91100 describes haptic feedback interface devices using electroactive polymer (EAP) actuators to provide haptic sensations and/or sensing capabilities. A haptic feedback interface device is in communication with a host computer and includes a sensor device that detects the manipulation of the interface device by the user and an electroactive polymer actuator responsive to input signals and operative to output a force to the user caused by motion of the actuator. The output force provides a haptic sensation to the user.
Further, WO 2012/063165 describes a user interface which comprises a touchable interaction surface formed by an array of actuators. The actuators are activated (i.e. moved out of the plane of the surface) in a coordinated manner such that they provide a haptic feedback to the user.
However, it is desired to provide a user interface which responds directly to an applied stimulus so as to provide improved feedback to the user and which allows wholesale changes to the surface.